E-bike basics: The most important key figures about the electric drive

Performance

Specified in watts (W). The rated or continuous power, which is specified as 250 watts for most motors, is merely a theoretical value. In reality, the peak power determines how hard a motor can push - and this can be significantly higher. The peak power applies under ideal conditions, i.e. in the highest support level and at an optimum speed. The motors usually only deliver maximum power at pedalling frequencies of 75 to 90 revolutions; rear wheel motors require a certain minimum speed for this.

Support factor

This is given as a percentage and expresses the ratio of the motor power to the rider's own power. The factor increases with the assistance level and can range from a fraction to a multiple of the rider's power: powerful motors such as the Bosch add up to 400 per cent of the rider's pedalling power in turbo mode - up to maximum power. The factor can usually be individually programmed for the various assistance levels via an app.

Torque

Specified in Newton metres (Nm). In practice, this mainly determines how strongly the bike accelerates over the first few metres. It is more relevant for gravel bikes than for road bikes, as it helps when overcoming obstacles, for example. The values are mostly around 50 Nm for mid-mounted motors. The figures for rear-wheel motors should be treated with caution: they are usually converted in order to be able to compare them with mid-mounted motors. In fact, they are significantly lower because the torque is applied directly to the rear wheel and there are no transmission losses. High-torque motors in particular can require careful handling on loose surfaces.

Battery capacity

Is specified in watt hours (Wh) and indicates how much energy is in the battery; this directly determines the range. For racing bikes and gravel bikes, 200 to 400 Wh is common. The capacity can be increased by around 50 per cent with an optional range extender - a smaller additional battery that is usually located in the water bottle holder. Whether larger capacities always make sense depends on the area of use, your own fitness level and your budget. Batteries are very heavy and very expensive.

Range in kilometres

This figure is only an estimate and should always be treated with caution. It depends on many influencing factors, such as the assistance level, the system weight and the percentage of incline. In the case of racing bikes, there is also the fact that the motor is often not active for large parts of the ride above 25 km/h.

Reach height

The figure in metres of altitude is more meaningful because it assumes that the motor is constantly delivering power. In practice, it is usually the metres in altitude that drain the battery. The reach height also depends on the support factor, system weight and the gradient. However, comparable values can be determined in standardised tests. With most road bikes and gravel bikes, riders weighing around 70 kilograms can expect to cover around 1,000 metres in altitude at the highest support level. At the lowest level, this can double, but then at a correspondingly slower pace.